I liked the way the letter started. It would be cool to see it finished. I would hold off on sending such a letter unless you want to limit contact with your MIL.
I am at an age when my mother-in-law's generation is no longer with us but I get religious emails from friends, family and sometimes total strangers. I usually just hit delete. However, I did have a thought in reading your dilemma since your mother-in-law knows how you believe. There is a place at the bottom of an email where you can plug in a permanent message. Maybe you could put something like, "I am a non-theist so would appreciate receiving no religious emails. Thank you." Maybe after your mother-in-law reads this a hundred times, she (and others) will finally get the message.
I very much like your not sent Email reply! I'm not going to judge you on your decision, or try to tell you what to do, because I don't know your circumstances well enough. Plus, I'm not a god-like advisor :)
However, for me and my circumstances (and personality), I would add some details, a few more statements about my appreciation for her concern (at the first of the Email), and send it!
Idaho Spud, I very much like your suggestion that I add at the beginning of that email some acknowledgement of my MIL's goodwill and genuine concern and my appreciation for her. She is, in fact, a very good person, not to mention that she is 85 and treats others with kindness at all times and has a sharp mind and excellent memory. In addition to that, we live in the same house, and she is very easy to get along with. How many people can say that about their MIL?
I ALMOST, but not quite, think that she might be able to read my comments and perspective with an open mind. (Please note-- my conclusion is that she ultimatley could NOT.) She might not reject me, but she could not, I believe, allow herself to see the logic of what I might have to say.
At 85, she is probably looking forward to seeing her dead family members in heaven. She won't, but why bother her with this information? Since I can't offer eternal heaven (yuck!) to others, I don't broadcast my beliefs unless asked -- or triggered by an attack of salvation. I think you're right to leave her to her fantasies. (But keep the letter; an occasion for it might arise later.)
I feel your dilema. My daughter in kindergarten was told she was going to hell because she wasn't a baptist. She was 5 & did not even know what the meaning of heaven or hell. She came home in tears & had nightmares for months. I would agree w/JW that since she is 85 why argue the point ?
They were conditioned from birth to conform. That was the norm. Her intentions are based on what she was taught. She just doesn't realize there are other points of view.